Epoxides are very important chiral building blocks for the synthesis of enantiomerically pure complex molecules. Asymmetric epoxidation of olefins presents a powerful strategy for the synthesis of enantiomerically enriched epoxides.
Among many epoxidation methods, chiral dioxiranes generated ill situ from an oxidizing agent and a chiral ketone have appeared to be promising reagents for asymmetric epoxidations. Since the first asymmetric epoxidation of olefins with dioxirane were reported in 1984, significant progress has been made in the area. A variety of cyclic chiral ketones have been used as catalysts to achieve enantioselectivity for the epoxidation of olefins.
However, there is a still need for an inexpensive, readily available, and general asymmetric epoxidation catalyst which can epoxidize a variety of olefins, in particular for cis and terminal olefins, with high enantioselectivity.